1. Field of the Invention
This invention relates to a rope that provides electrical conductivity. In particular, the rope can be used as an electric fence to contain animals within an area or deter animals from entering an area.
2. Background Information
Several devices exist for the containment of animals. Permanent fences made of wood or metal are resilient, but require an expensive and complicated installation. Often a situation will necessitate a non-permanent fence, such as for restricting horses to graze in a portion of a field. Electric fences can be a non-permanent barrier or a long-term solution for cordoning off an area and providing an effective deterrent to contain livestock or exclude wildlife.
Several criterion exist for the durability and characteristics of a good electric fence. Such a fence should withstand the weather, including snow, rain, hail, winds and sleet, especially as encountered in a Northern climate. The fence should also be UV resistant. If an animal brushes the fence, an immediate shock should be administered. Additionally, the fence should be supple and resilient in the event of a collision by an animal. Ideally, the fence should last for several years to avoid the hassle of constant replacement or repair. The ability to meet all of the above criteria is challenging for a fence typically constructed of weather-sensitive metal and pliable, degradable synthetic fibres.
Traditional electric fences combine metal and synthetic fibres to create a rope or a tape. Often, the metal wire becomes broken, either due to the collision of an animal with the fence or under deterioration caused by harsh climate conditions. Upon breakage, the entire fence loses effectiveness as the electrical circuit is interrupted. A tradeoff must be made between the strength of the metal and the conductivity of the metal. For example, copper has high conductivity, but is low in strength, prone to breakage and degrades quickly when exposed to outdoor climate conditions. Additionally, the use of inexpensive, substandard polyester will usually cause deterioration of the fence within 24 months, which is a relatively short timeframe to require replacement of the fence. Related to the type of metal and synthetic fibres used, the thickness of the fence must also be balanced with the weight of the fence since a thicker fence will withstand collision better, but will be heavy and may have installation issues.
U.S. Pat. No. 4,861,645 teaches a fencing tape with electrically conducting wires. The flat electrifiable fence has at least two conductive wires running through the length of the tape with bridges between the wires to provide conductivity in the event of a wire breakage. In the preferred embodiment, the tape is made of polyolefin and the wires are stainless steel.
U.S. Pat. No. 5,036,166 teaches an electrical fence line that can be a tape or a rope. The non-conductive material is of high strength and high visibility and is either woven, braided or twisted with the conductive material. The conductive material consists of two wires, one highly electric with low strength, such as copper, and the other of high strength, incurring a higher resistance, such as stainless steel. The wires touch either continuously or intermittently along the length of the fence.
U.S. Pat. No. 6,341,550 teaches an electric fence with a braided exterior layer that is constructed of several conductive and non-conductive elements, each comprised of individual twisted strands. An optional inner core of non-conductive elements exists to create a rope made of mainly non-conductive elements. The conductive elements consist of one or more conductive strands combined with non-conductive strands. The conductive elements can alternatively contain solely conductive strands. A rope comprising two conductive elements is the preferred embodiment with the first conductive element braided in a counter-clockwise helix and the second conductive element braided in a clockwise helix. Half of the remaining non-conductive elements are wound clockwise, the other half, counter-clockwise. The tightness of the helix is variable depending on the amount of give required in the rope—tighter coils allow more give in the rope. The purpose of the double helix is to protect the low strength conductors from tensional strain since the helical structure allows the copper to uncoil as the rope is stretched until the outer fibres clamp down on the inner core.